In processing good quality iron ore in lump form to obtain higher iron content materials, such as steel and the like, generally two separate reactors are employed. The processing steps of drying, preheating, reducing, cementation, melting and refining of said ore are conventionally effected in one reactor, i.e., in a blast furnace, to produce pig iron. Subsequently the pig iron is processed in another furnace to provide molten steel.
In processing pulverized iron ore materials, the various processing steps such as drying, preheating and reducing the ore generally are effected in several distinct reaction zones provided in the same or separate reactors. For example, pulverized ore frequently is dried and preheated in a separate reactor or ore preheater. Next, the preheated ore is reduced by passing through a series of fluidized reduction zones, often provided in a single reactor. Thereafter, the finely-divided partially reduced ore is compacted in the form of briquettes. Then, briquettes are cooled under controlled conditions to prevent reoxidation of the reduced iron ore. Finally, the briquettes are ultimately utilized in steelmaking furnaces to produce molten steel.
Prereduced finely-divided iron ore is compacted for a variety of reasons including some relating to handling and storage of reduced metals. However, when the prereduced ore is to be charged in a blast furnace for subsequent processing, generally it is considered absolutely necessary that the prereduced ore be in a compacted form. Finely-divided prereduced ore would be swept out of a blast furnace by the heat reducing gases generated in the furnace.
Some processes have been suggested in the art for combining the reduction of pulverized iron ore containing materials with a melting and refining step to provide a more direct process for obtaining iron-containing materials.
In general, the combined reduction and melting of pulverized iron ore solids known to the art requires the use of a separate gasification zone in which either a reducing gas is generated by partially reacting a carbonaceous material with oxygen or steam, or a combustion gas from the melting zone is upgraded to provide a gas of sufficient reducing power with respect to the ore to be processed. Also, such process requires the use of special reactors to recycle and prevent the loss of finely-divided ore which is swept out of the melting furnace by hot combustion gases generated there.